During a White House meeting last week, a group of governors asked President Bush and Marine Gen. Peter Pace, chairman of the Joint Chiefs of Staff, about their backup plan for Iraq. What would the administration do if its new strategy didn't work?

The conclusion they took away, the governors later said, was that there is no Plan B. "I'm a Marine," Pace told them, "and Marines don't talk about failure. They talk about victory."

Pace had a simple way of summarizing the administration's position, Gov. Phil Bredesen (D-Tenn.) recalled. "Plan B was to make Plan A work."

In the weeks since Bush announced the new plan for Iraq -- including an increase of 21,500 U.S. combat troops, additional reconstruction assistance and stepped-up pressure on the Iraqi government -- senior officials have rebuffed questions about other options in the event of failure. Eager to appear resolute and reluctant to provide fodder for skeptics, they have responded with a mix of optimism and evasion.

Even if the administration is not talking about Plan B, the subject is on a lot of minds inside and outside the government. "I would be irresponsible if I weren't thinking about what the alternatives might be," Defense Secretary Robert M. Gates acknowledged last month to Congress, where many favor gradual or immediate withdrawal.

Gates did not elaborate. Several administration officials, while insisting that a wide range of options was discussed before Bush's Jan. 10 announcement, firmly closed the door on the subject of fallback plans. "I don't think anyone is going to be inclined to discuss any contingency-type planning," said National Security Council spokesman Gordon Johndroe.

National security experts outside the government have stepped into the void, offering detailed options through public papers, speeches and policy proposals over the past several weeks.

"The ultimate Plan B is pull everybody out," said Stephen D. Biddle, a senior fellow at the Council on Foreign Relations and an adviser to the Defense Department. "Nobody wants to do that. Most are looking at the middle ground between surge and pullout."

Most options involve partial or complete U.S. redeployment from Baghdad and other violent urban centers, followed by containment of the civil war within Iraq's borders -- keeping out meddlesome neighbors such as Iran and preventing a wider, regional conflict. Retired Marine Gen. Anthony Zinni, a former chief of Central Command, the U.S. military headquarters for the Middle East, said Congress is "drifting toward containment" and predicted that option will soon begin gaining popularity.

Daniel L. Byman and Kenneth M. Pollack of the Brookings Institution last month released the most comprehensive public exploration of containment. The two national security experts seemed to wince even as they proposed keeping up to 80,000 troops along Iraq's borders, cautioning that "there would be no end in sight either for the war or for their mission." But it is "the only rational course of action," they wrote.

"I firmly believe that is where we should wind up, and is what we should be doing now," said retired Air Force Gen. Charles F. Wald, formerly the No. 2 U.S. officer in Europe.

One military officer involved in long-term planning for Iraq said he does not think the idea is feasible. "It would be a massive operation," the officer said. "But having said that, it's probably the best option if they go into open civil war."